Influence mechanism of vertical loading mode on pile lateral stress and pile side resistance behavior

In order to study the influence of vertical loading mode on pile side resistance,the additional pile lateral stresses induced by the vertical load of pressing down and pulling up at pile top and pushing up at pile bottom were analyzed with numerical simulation method.It is shown that the additional pile lateral stress under pressing down at pile top is compressed stress,and those under pulling up at pile top and pushing up at pile bottom are tensile stresses 15 -20 m under pile top and ±2.5 m from interfaces of soil layer are the main distribution areas of additional pile lateral stress.The max reaches more than ±80% of pile lateral stress due to soil self-weight,but stress gradient along the depth is great.Influence of soil kind,pile length and pile diameter on the additional radial stress can not be ignored.According to the relation between pile lateral stress and pile side resistance,the influence of vertical loading mode on pile side resistance is discussed.It is unreasonable that the pile side resistance under pressing down at pile top multiplied a coefficient is regarded as that under pulling up at pile top and pushing up at pile bottom in spite of soil location,pile length and pile diameter.